International commerce requires the transportation of goods throughout the world. In the present world economy, an increasing supply of goods are transported on ships. Many of the ships used to transport goods are large ocean-going ships. One unfortunate result of the increase in ship traffic is an increase in ship damage due to collisions or running aground. Some of these accidents require major repairs, which forces the ship to be placed in a dry-dock for repairs. Dry-docking a ship is a very costly procedure that is unavoidable in accidents requiring major repairs.
However, some accidents do not require major repairs. Often the only damage sustained by a ship running aground or striking a floating log is a bent propeller. The repair of a propeller itself may be a simple task, but there is presently no device that easily can repair the propeller under water. Some prior art attempts to repair a propeller under water involve a wrench and a long pry bar, but there is no readily available position from which to exert a force on the pry bar. Therefore, the ship must be placed in dry-dock to effect repairs even though the repair itself may be simple. Once the ship is placed in dry-dock and the water drained away from the ship, the propeller may be straightened by pressing it back into its original shape. The cost of the repair is relatively small when compared to the cost of placing the ship in dry-dock. Furthermore, the ship is taken out of service for a prolonged period of time in order to place it in dry-dock. The cost of removing a ship from service may exceed the cost of placing the ship in dry-dock
If the propeller is removed or repaired in dry-dock, prior art attempts to repair a propeller often involve heating and bending the propeller, often with a large press ill-suited for the task. Bent portions may be removed from the propeller because prior art equipment cannot straighten the propeller with the necessary precision.
Prior art attempts to use an arbor press for propeller straightening have failed because the arbor press typically has opposed inner surfaces of substantially equal length as seen in FIG. 1. This configuration applies pressure to the propeller between the ram 1 and a flat surface 2. Pressure is applied at only two points by the ram 1 and the pad 2. A large pressure is required to bend a propeller using an arbor press in this manner. Therefore, the arbor press must be large and have a significant amount of reinforcement to prevent the arbor press from shining when the ram 1 is activated.
Some machine shops place a long metal bar 3 on the flat surface 2 to extend the working surface and allow a large object such as a propeller to be straightened. The metal bar 3 is cumbersome and may not direct the forces in the desired manner. Some arbor presses use a large bench as the flat surface 2. This approach requires that the propeller be secured to the bench at a precise angle. All of the prior art approaches to propeller straightening are cumbersome and require a great deal of time. The propeller must be precisely manipulated, and the pressure applied by the ram 1 may not be adequately positioned to effectively straighten the propeller.
Therefore, it can be appreciated that there is a significant need for an apparatus and method for propeller straightening that may be used underwater.